The present invention relates generally to electric vehicles, and more particularly, to a system and method for controlling a surface-mounted permanent magnet synchronous machine drive used in electric vehicles over a wide speed range using a regulation error in the torque producing current component.
The assignee of the present invention designs and develops electric vehicles employing surface-mounted permanent magnet synchronous machine drives. One operation that is required when controlling such machine drives is flux weakening which is when the machine drive operates above base speed.
One straight-forward approach is to employ a number of look-up tables to resolve flux weakening operation. In order to achieve results and performance similar to those of the present invention, the straight-forward approach mentioned above requires creation of numerous and cumbersome data structures within the look-up tables to handle all possible situations in the system and its environment.
A method presented in a paper authored by S. D. Sudhoff, K. A. Corzine, and H. J. Hegner "A Flux-Weakening Strategy for Current-Regulated Surface-Mounted Permanent-Magnet Machine Drives", in IEEE Transactions on Energy Conversion, Vol. 10, No. 3, September 1995, pp.431-437 proposes a flux weakening strategy. The Sudhoff et al. approach requires usage of "bang-bang" (hysteresis) current regulators. This is not acceptable in automotive applications due to the varying switching frequency, and this way induced electromagnetic interference.
It would be desirable to have a method that does not rely on a cumbersome set of look-up tables, and wherein automatic transition is accomplished at all operating conditions. It would be desirable to have a method that does not require measurement of the DC bus voltage. It would be desirable to have a method which does not require usage of "bang-bang" current regulators.
It is therefore an objective to provide a system and method for controlling a surface mounted permanent magnet synchronous machine drive over a wide speed range using a regulation error in the torque producing current component. It is also an objective to provide a system and method for controlling a surface mounted permanent magnet synchronous machine drive used in electric vehicles.